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STUDY ON OPTICAL SPECTRA OF Cr3+ IONS IN PHOSPHATE, FLUOROPHOSPHATE AND
FLUORIDE GLASSES
G. Fuxi, L. Huiming
To cite this version:
G. Fuxi, L. Huiming. STUDY ON OPTICAL SPECTRA OF Cr3+ IONS IN PHOSPHATE, FLU-
OROPHOSPHATE AND FLUORIDE GLASSES. Journal de Physique Colloques, 1982, 43 (C9),
pp.C9-303-C9-306. �10.1051/jphyscol:1982955�. �jpa-00222484�
JOURNAL DE PHYSIQUE
Colloque C9, supplement au n°12, Tome 43, decerribre 1982 page C9-303
STUDY ON OPTICAL SPECTRA OF C r3 + IONS IN PHOSPHATE/ FLUOROPHOSPHATE
AND FLUORIDE GLASSES
G. Fuxi and L. Huxming
Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, China
Résumé. - On mesure l'absorption, la fluorescence et la durée de vie des 3+ 3+ -
ions Cr , Mo dans trois espèces de verrez en base, analyse et calcule des données de spectre basées sur la théorie du champ coordinateur. En outre, on étudie l'excitation du laser et le spectre d'émission de resolution dans le temps, discute la caractéristique spectrale et la structure de site dans le reseau d'ion Cr dans des verres. 3+
A b s t r a c t . - Absorption, fluorescence and lifetime measurements of Cr , 3+
Mo ions in three kinds of glass bases have been performed. Analysis and 3+
calculation of the spectral data based on the ligand field theory have been carried out. Furthermore, laser excited and time resolved emission spectra
3+
have been studied, spectral characteristics and site structure of Cr ion in glasses are also discussed.
Recently, a great attention has been paid to the transition element ion doped 3+ 3 glasses for the development of tunable solid state laser, among them Cr (3d ) ion is the most important one. The absorption spectra of Cr has been studied exten-3+
Tl-31
sively in many glass systems'- , but a few work has been done for fluorescence and relaxation spectra, there is still an argument about the fluorescent transition of Cr in glasses'- ' . We have investigated the spectroscopic characteristics of Cr in phosphate, fluorophosphate and fluoride glasses'- . The measured and cal- culated peak wavelengths of absorption bands, their optical transitions, Racah parameter B and ligand field strength Dq of Cr ion in glasses are listed in Tab.l. 3+
The calculated results based on the ligand field theory are consistent with those obtained from the experiments. The temperature dependence of fluorescence spectra and lifetime of Cr doped glasses are shown in Fig.l and 2. The peak wavelengths 3+
of fluorescence of Cr in phosphate, fluorophosphate and fluoride glasses are 3+
11290cm , 11520cm" and 11680cm" respectively. It can be found that in order of phosphate—fluorbphosphate--fluoride glasses, the ionic contribution of the chemi- cal bond between the central activated ions and ligands increases gradually with the increase of Racah parameters B. The corresponding peak positions of absorption spectra, as well as those of fluorescence spectra shift to the shorter wavelengths.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982955
C9-304 JOURNAL DE PHYSIQUE
Tab.1 Measured and Calculated Absorption Peak P o s i t i o n , Correspondent T r a n s i t i o n and Parameters 6, Dq o f
cr3+
and Mo3+ i n Glasses4~ 29 - 4 ~ l!3 ( P ) 4 ~ 2 g - 4 ~ l g ( ~ ) 4 ~ 2 g - 4 ~ 2 g 4 ~ 2 g - 2 ~ ( G )
Ions Meas. Cal
.
Meas. Cal. Meas. Meas. lODqB
Phosphate 33400 33700 21900 21600 15100 14500 15100 667
Cr3+ Fluoro-
phosphate 34200 34590 22600 22200 15400 14700 15400 706
Mo3+ Phosphate
- -
27900 27910 22400 15800 22400 500a. Phosphate glasses b. Fluorophosphate glasses c. F l u o r i d e
1) 80K 2) 109K 1) 91-124K 2) 156K 1) 85K
3) 153K 4) 204K 3) 189K 4) 237K 2) 176K
Fig. 1 Temperature Dependence o f Fluorescence Spectra of
cr3+
i n GlassesThe experimental r e s u l t s a l s o show t h a t t h e increase o f fluorescence i n t e n s i t y , l i f e t i m e and weakening o f temperature quenching e f f e c t o f glasses from phosphate t o fluorophosphate can be considered as t h e decrease o f n o n - r a d i a t i v e t r a n s i t i o n p r o b a b i l i t y . As a compari
-
3+ 3 son absorption and fluorescence spectra o f Mo (4d ) i n phosphate glass have a l s o been studied. The e x p e r i - mental r e s u l t s are shown i n Tab.1 and Fig.3.
Fig.2 Temperature Dependence o f Fluorescent L i f e t i m e of
cr3+
i n Glasses1) F l uorophosphate glasses 2)Phosphate glasses
There i's an argument about the f l u o r e s c e n t t r a n s i t i o n o f
cr3+
i n glasses, because t h e upper energy l e v e l s,.
'T and 'E a r e very c l o s e t o each o t h e r . Compared
2 9 9
w i t h t h e fluorescence spectra o f Mo3+, t h e emission from
cr3+
doped glasses i s c h a r a c t e r i z e d by i t s wider bandwidth (2500-3000cm-~) and s h o r t e r l i f e t i m e (-50ns), i t belongs t o t h e spin-allowed t r a n s i t i o n . So we consider t h a t t h e l i g a n d f i e l d s t r e n g t h Dq o f Mo 3+i n glasses i s l a r g e r i n comparison w i t h t h a t o f Cr3+, t h e near i n f r a r e d emission i s c o r r e l a t e d w i t h T4 ~ ~ f o r -
cP3+
~ Aand 2 ~ g - 4 ~ 2 g ~ ~ f o r ~ 0 ~ ' .Furthermore, 1 aser e x c i t e d fluorescence o f
cr3+
i o n i n glasses has been i n v e s t i g a t e d . We used d i f f e r e n t l a s e r wavelengths f o r e x c i t a t i o n , such as 0 . 5 1 0 6 ~ and 0 . 5 7 8 2 ~ (copper vapor l a s e r ) , 0.57-0.62~ ( f l a s h lamp pumped dye l a s e r ) and 0 . 6 3 2 8 ~ (He-Ne l a s e r ) . The l a s e r e x c i t e d emission spectra o fcr3+
i n fluorophosphate glasses a r e shown i n Fig.4. Only small v a r i a t i o n i n 4 ~ 2 g - 4 ~ 2 g fluorescence c o u l d be noticed.T h i s agrees w i t h the r e s u l t s measured by Brawer and whiteL7]. I t i s e v i d e n t t h a t s i t e t o s i t e v a r i a t i o n i s n o t s e n s i t i v e t o l a s e r e x c i t a t i o n due t o the phonon- photon c o u p l i n g a s s i s t e d energy l e v e l broadening and t h e dependence o f energy gap between e x c i t e d and ground s t a t e s on Dq value.
Fig.3 Temperature Dependence Fig.4 The Dependence o f Fluorescence o f Fluorescence Spectra o f Spectra o f
cr3'
i n Fluorophosphate bIo3+ i n Phosphate Glasses Glasses on t h e E x c i t e d Laser Wavelength1) 92K 2) l l O K 1) broad band AE=0.85vm AAL=192nm
3) 173K 4) 249K 2)5106A Cu l a s e r 0.84 176
3)5782A Cu l a s e r 0.836 173 4)6328A He-Ne l a s e r 0.834 185
Then we p u t more emphasis on t h e measurement o f time resolved and l a s e r e x c i t e d emission spectra. A f t e r l a s e r e x c i t a t i o n a group o f
cr3+
i o n s absorbed l a s e r l i g h t and s t a t i s t i c a l l y d i s t r i b u t e d a t t h e e x c i t e d s t a t e . I n t h e p e r i o d o f r e l a x a t i o n somecr3+
i o n s i t e s w i t h l a r g e r energy gap between 4~ - 4 ~ s t a t e s o r w i t h l a r g e r29 29
Dq value possess longer l i f e t i m e , so t h a t they emit l a t e and t h e i r fluorescence
JOURNAL DE PHYSIQUE
s p e c t r a s h i f t t o s h o r t e r wavelength r e g i o n . Fig.5 shows t h e t i m e r e s o l v e d and l a s e r e x c i t e d emission s p e c t r a o f
cr3+
i o n s i n f l u o r o p h o s p h a t e glasses t a k e n a t d i f f e r e n t decay t i m e . The f l u o r e s c e n c e l i n e n a r r o w i n g and peak wavelength s h i f t i n g can be c l e a r l y observed. The emission s p e c t r a move t o s h o r t e r wavelength r e g i o n w i t h l o n g e r decay t i m e a f t e r e x c i t a t i o n .cr3+
i o n s i t e s e x c i t e d by 5106A l a s e r l i n e ( l o c a t e d a t t h e l o n g e r wavelength s i d e o f 4 T a b s o r p t i o n band) possess1 g
s m a l l e r Dq v a l u e and e x h i b i t more ob- v i o u s l i n e n a r r o w i n g and s h i f t i n g F i g . 5 Time Resolved Spectra o f C r 3+
e f f e c t t h a n those e x c i t e d by 5782A i n Fluorophosphate Glasses l a s e r l i n e ( l o c a t e d a t s h o r t e r wave- ( Cr203 0.5% wt, room temperature ) l e n g t h s i d e o f 4~ a b s o r p t i o n band) which possess l a r g e r Dq v a l u e . Laser 2 9 l i n e of 6328A i s a t t h e c e n t r a l p a r t o f T 4 a b s o r p t i o n band, i t s e x c i t e d emis- s i o n s p e c t r a i s s i m i l a r t o those o f broad band e x c i t a t i o n due t o o v e r l a p p i n g 2 9 t r a n s i t i o n o f d i f f e r e n t
cr3+
s i t e s . So t h a t t h e l a s e r e x c i t e d and t i m e r e s o l v e d f l u o r e s c e n c e l i n e n a r r o w i n g i s a u s e f u l t o o l f o r s t u d y i n g t h e s i t e s t r u c t u r e o f t r a n s i t i o n element i o n s i n glasses.References
[I] BAMFORD C.R., Phys. Chem. Glass., z ( 1 9 6 2 ) 189.
[2] BATES T., "Modern Aspects o f t h e V i t r e o u s S t a t e "
E d i t MACKENZIE J.D., 1962,
2,
chap.5, B u t t e r w o r t h e s , London.[3] GAN FUXI, J. Chinese S i l i c a t e Soc., fj(1978) 41.
[ 4 ] KARAPETYAN G.O., KOVALYOV V.P., LUNTER S.G., Opt. & Spect.
19(1965) 951, (Russian).
-
[5] SHARP E.J., MILLER J.E., Phys. L e t t . , m ( 1 9 6 6 ) 142.
[6] GAN FUXI, L I U HUIMING, A c t a O p t i c a S i n i c a , z(1982) [7] BRAWER S.A., WHITE W.B., J. Chem. Phys., E ( 1 9 7 7 ) 2043.
